Add method to convert paths to globs

[sindresorhus]

The change in 3.0.0 that changed it to only allow forward slash paths turned out to be a pain. Anywhere I use fast-glob, I now need to specially normalize paths on Windows.

Would be useful if fast-glob had a .convertToGlob() kinda method, with similar logic to sindresorhus/del@01da91f#diff-168726dbe96b3ce427e7fedce31bb0bcR41-R53.

Maybe there could even be some kind of option to loosen fast-glob, when you don't need glob escaping, but do need to accept both file paths and globs, which is actually the majority of cases, at least for me.

[mrmlnc]

Fixed in the master by #392. Will be shipped with 3.3.0.